so, Grid is now deprecated. I thought I would try and embrace
the new constraint layout API. One of my use cases of Grid is to
dynamically create and remove rows based on user input. I tried to
do the same thing with ConstraintRow and was successful. However,
it get's really slow after a couple of new row additions. compile
using FB 3 B2. click on "make new row" button a couple of times and
you'll see what I mean.

If anyone has any insight on how to make this not suck, it
would be
greatly appreciated.

This was cross posted to flexcoders and Peter was kind enough
to answer over there.

Answer: update to a nightly build. I was using the stock SDK
which came with Flex Builder 3 Beta 2. Updated to nightly build
#187237 and everything works. Not sure what the minimum nightly
build number is to fix this issue.